Bellows type envelope having all edges of mouth reinforced



Feb. 8; 1949.

M J. SHAFFER BELLOWS TYPE ENVELOPE HAVING ALL EDGES, OF MOUTH REINFORCED Filed March 8, 1946 FIG].

Patented Feb. 8, 1949 UNITED PATENT OFFICE BELLOW-S TYPE" ENVELOPE HAVING ALL .EDGES OF .MOUTH'REINFORCED Morton J. Shaffer, New York,.N. .Y.

Application'MarchS, 1946, Serial No. 652,940

iacflaim. 1 .This invention :relates to improvements in envelopes, and .has particular relation to envelopes of the expansible "and collapsible type, especially pseudo :envelopes of large "sizeiadapted for use as document or other-filing containers.

Envelopes or containers 'for use fin'filing cabinets, especially those of large dimensions,1are subject to olifiicult conditions of service. Since they serve for the accumulation of documents, etc., partaining to individual-persons or subjects, theenvelope 'needs to be of the expanding type if the documents, etc, are to be properlypreserved; hence, a really serviceable envelope for the purpose needs tube of the bellows fold type-capable 'of expanding uniformly through-' out the height and width of the envelope without materially changing its overall dimensions.

While someffo'rrnsof envelopes-for the purpose employ flaps, thus protecting the marginal "edge or edges of the open side-th'e-flapextendsover the open side and'is =itself positioned at such side of the envelope; but the use of a nap on envelopes of the expandible'type is diflicult since the fiap must also be capable of expanding, a condition which is not only 'difiicult to produce, but if absent, provides for rapid wear since the constant change in the line oi fold provides rapid deterioration. Because of these conditions, flaps are preferably omitted, andrelianoe'placed on the cabinet to protect'the contents;' butthe omission of the flap leaves the marginal edges exposed and, unless re-iniorced, vulnerable toth'e effects of continued handling,

Another of the difficulties in the use "ofsuch envelopes is the fact'th-at as the accumulations continue, the file increases in thickness, and while the "bellows fold may compensate in this-respect, such increase also. increases the'distance'between the outer plies of the envelope at the sides and bottom; the increase at the sides does not materially afiect the conditions, but the increase in distance at the bottom provides increased spacing of the bottom supporting edges while the intervening bellows fold :remains'out of contact with the bottom of the cabinet drawer, (thus tending to produce conditions .of instability of the file after a considerable accumulation of contents is had since the weight of the fileand its content is applied on such spaced edgesywith the bellows fold extending into :both side and bottom edges, the spaced s'edgestend to beindependent, and thus permit the instabillty oonditions to develop.

Another of the conditions present is that '..Of developing an envelope to :meet and overcome 2 these conditions, with an' arrangement such 'that itrcan be producedffrom a single blank, especially Where the blank is to be fashioned in'totheprodnot simply by folding and adhesively connecting certain'oi its parts. An envelope for thisservice to be of long-life characteristic and possess the stability that is :a desired essentialmustube formed of strong :iieavy material, .a condition which, in presence .of the bellows-fold characteristic, places a severe strain upon the .fold lineswhere the action stimulatesto-some extent avhinging actiomto obtain the necessaryreiniorcing action without the use of separate 're-inforcing blanks or material presents a somewhat difficult problem in first developing the wayof solving'the problems previously referred: to and to then fashion a blank which .canbefolded insimple'm-anner and adhesively secured in its product form and wherein the blank,'when soiolded and secured, willprodoes such solution way.

The present invention has for its object the production of an envelope of this type, produced from a blank "by foldingand adhesively-securing certain of its parts, and'whic'h, when completed, will provide a solutionto the :problems indicated, and provide an envelope of comparatively lowcost characteristic, having the 'expansible and collapsible condition, and which is capable of withstandingrough service usage without imaterially affecting its servicealoility.

To these and other ends, the nature of which will :be more clearly understood as the invention is hereinafter more fully'disclosedsaid invention consists in the improved construction and com-r bination of .parts hereinafter more fully described, illustrated in the accompanying'drawlugs, and more particularly pointed out in the appended claim.

In the accompanying drawings, in which similar reference characters indicate similar parts in each of the views,

Eigure' l is a plan view of oneform'of blank employed in the present invention.

Figure 2 is a perspective view of an envelope resulting "from the folding of the blank of Figure 1 and the adhesive connection of certain of its parts;

Figure 3 is a vertical sectional view of the envelope taken on line 3--3 of Figure 2.

lFigures 4, 5, 6 and 7, are detail sectional-views taken on lines 4-4, "5-5, Iii-6 and '1-,-"'|,"respectively, of Figure 2.

For the purpos'e of identifying the various walls of the envelope in the following description, it is assumed that the envelope is being utilized for filing service, in which, following the usual practice, the wall carrying the identifying indicia is the rear wall of the envelope which carries a tab or the like upon which the indicia is exposed above the front of the envelope, the content of the envelope being located between the front and rear walls with the identifying indicia facing the front of the drawer of the filing cabinet.

The blank utilized in the production of the envelope is shown in Figure l, in which the rear wall is shown at H), with the front wall indicated at l 4. Between these walls is the bottom 12, 0, indicating the folding line between the rear wall Hi and bottom l2, a indicating the folding line between the front wall I I and the bottom [2, while a2 indicates an intermediate folding line between lines a and a, thus dividing the bottom 12 into two zones l2a and i2b which-with the front and rear walls I i and |-provide the bellows; fold formation for the bottom of the envelope, the zones 12a and 12b being juxtaposed, respectively, to walls i0 and H in producing the bellows fold and with the envelope collapsed.

The wall has an extension I'Jaat each of itsopposite sides, the extension being of a width approaching that of zone lZa, the extension having its direction of length less than the height of wall It], with the extension extending substantially fromthe folding line a to a point spaced from the opposite end of the height of the wallthe height being the distance between line a and a line b which is parallel to and opposite line a; the upper zone of wall It] is designed as the indicia-carrying portion of the envelope, the length of extension lfla presenting the depth of the content-receiving portion of the envelope; the portion of wall I0 above the upper end of extension it) presents the tab or indicia-receiving zone, which is preferably formed with rounded corners to provide a finished appearance.

.Since .such indicia-bearing zone is to be strengthened by reinforcing, the wall carries, beyond line b a top extension which is substantially a reversed replica of the adjacent portion of wall If! and its extension Illa, extension lab being folded forwardly on line 17 into overlying relation to the upper portion of wall, it and adhesively secured thereto, thus providing a strengthened reinforced indicia-bearing or tab zone, the thickness in thiszonerepresenting two plies of the sheet material of the blank, which two-ply thickness also extends into the. upper zone of extensions Illa-actually the two-ply thickness reaches materially below the tab zone, the distance being represented by the length of extensions "lab of extension lBb, with the two-ply thickness also provided by the extensions lab secured to the upper portion of extensions Illa.

Wall H, which lacks the tab zone, is, however, also provided with a reinforcing extension lib, foldable inwardly on to wall I I on line 0 and adhesively secured to the wall. Wall i I also carries extensions-Ha at opposite sidescorresponding to extensions Illa, these having a length equal to the height of wall II and of its extension lib; in addition, wall H carries beyond extension Ila, an additional-extension He, the two being dis-- tinguished by folding line d; the portion of extension Ilc beyond folding line c may have its outer edge cut away as shown.

In the envelope assemblage, extensions lilo and Ho form walls of the side bellows foldsimilar to zones I20! and I21); however, since the extensions are not integral, as are zones Ma and lib,

' 4 they must be connected, a function which is provided by extensions Hc which are folded on line d into overlying relation to extensions 10a to which they are adhesively secured, line it thus becoming the mid-position folding line of the side bellows fold. After the side bellows fold section is thus formed, the reinforcing extension I'lb is then folded inwardly on to wall l I and adhesively secured: thereto,'the portions ofv extension lib corresponding to extensions Ha and |ic--indicated at ab and Hbc-being adhesivcly secured to the inner face of extension Ho and the exposed face of inturned reinforcing portion limb.

By this arrangement, the entire upper marginal Zena-including the tab zone-of the envelope is reinforced, portions of the side bellows fold portion of such margin being of two-ply thickness, while other portions are of three-ply thickness; the folding line 11 portion of the marginal zone is at least of two-ply thickness within this zone. Hence, the entire upper marginal zone of the envelope is reinforced, with the reinforcing members adhesively secured; not only does this strengthen the envelope, but the adhesive securing of the marginal zone prevents the formation of pockets into which papers could extend and be difficult to remove.

The length of the bottom l2 equals that of the front and rear walls. The ends of the bottom, however, carry tab extensions 120, each having a length approximating that of the combined width of extensions i la and He; the tab extensions may be of equal width with the bottom i2, but are preferably of decreased width with the width symmetrical to folding line a2 which is continued throughout the length of the tabs (the side walls may be inclinedto give the tabsasomewhat tapered appearance, as shown). In forming the envelope, these tab extensions are folded on the line ewhich constitutes the folding line of extensions 3a and Ha-after extension lfla has been foldedthus placing the tabs in overlying rela tion to the lower end of extension 10a, to which the tab is adhesively secured to the outer side of the extension, the overlyin relation extending to folding line a2, the portion of the tab on the oppositeside of line a2 being secured in underlying relation to the inner side of extension Ha, and also in underlying relation to extension No to the extent of the width of the latter. The tab is thus fixedly secured to both the front and rear walls of the envelope with folding line a2 of the tab underlying foldingline d at the side of the envelope, the outer face of the tab being adhesively secured to both extensions Ho and Ho. With the tab having a tapered formation as shown, this assembling just described; leaves a portion of one side of the tab exposed on the outer side of the envelopeand a portion of the opposite side of the tab exposed on the inner side of the envelope, with the tab actually positioned between the extensions of the front and rear walls of the envelope. Since line 12 presents the inter mediate folding line of the bellows fold of the side of the envelope, the extension of line a2 present in the tab becomes a portion of this intermediate folding line of such bellows fold.

The assemblage thus described completes the envelope formation with one exception-the bellows fold for the bottom l2. Thus far, the assemblage provides the folding of the blank and the securing of the side seam-like formation together with the side bellows fold. The latter presents a number of characteristics as indicated more particularly in Figures 4 to '7, inclusive. For

instance, asindicated in Figure 5, the intermediate portion of .the side bellows fold is mostly of single ply formationformed from the exten sions -lflaand Ha, but the extension llc of the latter :extends across intermediate folding line :1 into overlapping 'relation'to extension Ella; since the latter does not cross folding line d the latter isof single ply formation while the overlap provided by extension Ilc-which is the securing extension-provides a double-ply formation. Hence, the bellows fold is not only strong but has the essential flexibility needed for such service.

its indicated in Figure 7, the arrangement referre'dto continues to the top of the envelope with certain additions which are now referred to: "Since extensions lflh and lib are infolded onto their respectivewalls, as indicated in Figure*3, the upper marginal zones of the front and rear walls are of two-ply formation due to the reinforcing provided by extensions lab and lib. But theitop marginal zones of the side bellows fold are also reinforced by the tab extensions Hla'b, flab-and Hbc. Tab ital), being infolded, underlies extension Illa, while tab Nah, also infolded, underlies extension I id to the intermediate folding line d, while tab Hbc, also infolded with tab I lab, underlies tab lfiab. As a result, all parts of the top marginal portion of the side bellows fold are of at least two ply formationthis including the intermediate folding line, the seam zone, however, is of four-ply formationmade'up'of tab lDab infolded on to extension ltd, the member He with tab ilbc then infolded on to'positione'd tab l'llab, thus firmly uniting I" the sides of the envelope within the bellows fold and at the same time providing a marginal reinforce-also secured-to the top of such fold, but without unduly increasing the thickness of the intermediate folding line in the marginal zone, the latter remaining of two-ply formation.

As with the top marginal zone of the envelope, the lower end zone of the side bellows fold includes the basic seam arrangement shown in Figure 6,; however, like the top marginal zone, the lower zone'carries additional features which vary to-some extent the arrangement of Figure 5, the variationsbeing brought about by the fact that in this zone the bottom 52 integrally connects the'front and rear walls, thus closing the bottom zone-in contrast with the open top, together with the presence of tabs lZc. Tabs E are bent upwardly on line f-which corresponds in position-with'folding line e of extensions Illa and Ilathic upward bending of tabs E20 being provide'd'be fore the adhesive connection of the lower zones of extensions Illa and He, the tab lZc extending between the latter, so that the tab overlies extension l0a-to which it is adhesively sccured-.and underlies extensions Ma and lie to which the opposite face of the tab is secured.

The tapered characteristics of tab I20 show the tablZc as not extending the complete distance to folding line e, leaving the folding line e of the assembly as of single ply thickness-as is the case throughout the vertical length of the side bellows fold, excepting the top marginal zone where the reinforcing extensions I Elb and Nb extend across line e and thus provide a two-ply thickness to line e within the top marginal zone. As heretofore pointed out, a portion of tab I20 is=exposed 'on the inner side of the side bellows fold, and a portion of the opposite side of the tabdisexposed onthe outer side of the side bellows folithese exposed portions lying on opposite sides of folding line alas extended into the'tab; Asa result, the intermediate folding line of the side bellows fold-corresponding "to line d- -:is of two-ply formation inxthis lower zone as Well as in the top marginal zone, with'the intermediate portion "of single 'ply formation.

The arrangement of the lower zone of the side bellows fold thus far described produces aparticular formation at the bottom of this fold-ea formation that is one of the important features of the invention. As will be'seen from Figure 1, the lower edge of extension Illa and the upper edge of extension Ha extend practically to folding lines a and a, ofthe bottom; since lines -a and a present the bottoms of the two walls 10 and l l which contact the support'the bottom of the filing cabinet drawer, for instance-the fact that these ends of extensions Ida and liq. reachto these lines as well, presents a structure in which the vertical length of the side bellows fold equals to extend over such extension ends, it is obvious that the lower end of the side bellows fold extends to the plane of the lower ends of walls I G and II, thus, in effect, producing a bottom zone of the envelope which not only contacts the support at the front and rear, but also at the ends, with the latter portion in the form of abellows fold which makes it possible for the envelope to expand and collapse to meet the service conditions without affecting the support-contacting conditions at the ends of the envelope. The advantage of this lies in the fact that regardless of the thickness of the accumulated envelope content the plane of contact of the envelope and support will remain constant, since the front and a rear of the'envelope in contact with the support on such plane are joined together by the lower end of the side bellows fold also in contact with the support on such plane, thus, in effect, pro-.

ducing a pseudo rectangular bottom to the envelope and in which the distance between the front and rear is variable at will without dis-' turbing these conditions.

Since, as hereinafter explained, the bottom also presents bellows fold characteristics, this arrangement provides for stability of an envelope of this type; it is well known thatwhere bellows folds are employed, there is a tendency to set up instability due to the fact that the .bellows fold leaves only opposing edges as supporting bases, with the intervening fold variable to vary the angles of the sides of the bellows fold, so that the bases can move relative to each other on the supporting plane-especlally where the accumulated content provides considerable spacing .between the front and rear; where the envelope is made up of several similar pockets, the instability is less apparent, since the intervening walls provide base support intermediate the front and rear-but where the envelope is of single pocket type, as shown herein, the instability is apparent from the above explanation. Hence, the connection of front and rear Walls on the contact plane by the lower portion of the side bellows fold is of definite advantage in providing the essential stability to the envelope, through prodmzing the effect of a pseudo rectangular support in all positions of the front and rear walls regardless'of the distancebetween these walls produced by expension or collapsing of the envelope in service.

'Thepresence of the structure just described,

however, affects the ability to provide the bottom bellows-fold through simply folding the bottom I! on lines a, a and A2; the latter course could be employed if the bottom ends of extensions Illa and H a, together with tab I20, were formed to omit the support characteristic and wall-connection provided by the side bellows fold produced by the use of the blank of Figure 1. Hence, the bottom bellows fold must be developed in presence of such end supports. This is provided by the use of the two folding lines 9 and it, these, with line 1, providing a triangular formationindicated as i2d-which is bisected by the portion of line a2 which extends through the triangle.

As will be understood, when the bottom and front and rear walls are folded to right angular relation on lines a and a, the full distance between the front and rear walls Ill and l I will be provided, at which time the side bellows fold becomes a planar formation in which line at lies in the plane of the sides represented by lines e, c, with line 1' representing line 6 in the bottom zone.

As such arrangement of content pocket is collapsed by developing the side bellows foldmoving folding line at inward relative to the end planar formationthe folding line a? of the bottom will also be moved inward relative to the bottom plane, to begin the collapsing of the bottom. While such movement of line a2 is produced throughout the length of bottom l2, that portion of line a2 lying between the apices provided by the meeting of folding lines g and it alone is active in forming the major intermediate folding line of the bottom bellows fold, due to the fact that line f of the triangle does not change relative to the bottom plank-shifting in such plane into the side bellows fold formationa condition which makes it necessary to concurrently develop the two folds g and h; this action, in effect, bisects the triangle 12d on line :12 to produce two smaller angles folded in opposite directions, with line a2 within the triangle becoming angular to the main portion of line (12, since the endof the line still remains in such bottom plane while the apex end moves with the remainder of the line, thus producing the angular relation, the latter, however, presenting a greater angularity through the fact that the side bellows fold is being concurrently developed, with line d-'together with the center of line f-also mov ing inward. And since the sides of the triangle represented by lines g and it remain in the respective planes of portions lZa and. 12b of the bottom, while line a2 within the triangle develops angularly, there is developed a variable space relationship between the inner face of the side bellows fold and the faces of the two smaller angles of the triangle; this space is maximum when the bottom and sides are fully expanded, and gradually decreases as the envelope is gradually collapsed, until it practically disappears when the envelope is totally collapsed, at which time the intermediate folding lines of the sides and bottom bellows folds, substantially meet interioriy of the envelope, but with the lower end zone of the side bellows fold exposed below the Walls of the bottom bellows fold and extending to the plane of the bottoms of the front and rear walls.

As a result the development of the corner zones at the bottom of the envelope presents a number of ply characteristics, depending somewhat upon whether the envelope is fully expanded, partially collapsed, or wholly collapsed. Basically, lines a, a and c2 of the bottom, independently of zone I2d, present single ply conditions, as to lines e of the side bellows fold-dine d of the latter also has this characteristic when the envelope is fully expanded; when partially or wholly collapsed, line d within the corner zone becomes of two ply formation, due to the fact that line c2 of zone IN is folded toward and into contact with line d (when fully collapsed) to form the lower zone of the side bellows fold which forms an end of the pseudo rectangle of the bottomthis dual ply formation is not a secured condition but provided by facial contact. Hence, in the partial or wholly collapsed condition, the lower zones of extensions Mia and Ha, not only have the secured conditions referred to above and indicated in Figure 6, but additionally have the ply formation of the latter increased by the approaching and facial contact of the two portions of zone 1211, so that this zone of the side bellows fold is made especially stable and not only provides a stable foot characteristic for the ends of the bottom, but also tends to preserve the definite pseudo rectangular formation, since this zone not only prevents the bottom of the front and rear walls from moving out of the seating plane of the envelope, but also prevents lateral movement of these walls relative to each other. These advantages are particularly valuable when the envelope is fully collapsed, at which time the overall distance dimension of the side bellows fold in the direction of front to rear is at its minimum-at such time, the parts pass into contact relationship to form a pseudo solid foot characteristic; as the envelope expands from such completely collapsed condition, the pseudo solidity is replaced by the skeleton formation provided by the opening out of the side bellows fold until the latter is made inactive as the envelope reaches its fully expanded condition.

Certain advantages result from the specific arrangement thus described, an important one of which flows from the fact that envelopes of this type capable of long and efficient service conditions, must be made from heavy paper stock capable of folding Without cracking at the line of fold; hence, the stock is of thick gauge and calendered highly. While it is possible to reinforce the lines of fold by the use of separate material of a thiner type, such as fabric, such addition, while adding strength, detracts from the appearance; where, as in the present invention, the

faces are securely adhered together by a hardened adhesive, any strains placed on the secured faces can weaken the adherent connection and thus make the envelope of short life characteristic. And, due to the fact that the side bellows-folds must be foldable, and are formed by the use of tabs thus secured together, renders this portion especially vulnerable.

The difficulty arises more particularl with the movable line of fold-the folding line which moves toward and from the plane of the fixedly-positioned lines of fold presented by the connection of the end tabs with the sides of the envelope, during the expansion and collapsing of the envelope.

The difliculty' The difiiculty can be understood from:

a 9 the factthat irithe mny ex anded position the connected flapspractically extend in such plane, while" the flaps, during envelope collapsing, extend angular to such plane, w th the median lineoffOId l3h movable "ne form-ing the apex of the angulari'elationship. If; in the expanded position, the inner resent the end presents a smooth connection betweenthe flaps or tabs, the-movement'of the movable line offold inward has the effect of forcing the apical Zone of the inner'plies of amulti-plylin-e of fold, toinfinite require a greater amount of material to compensate for the thicknessesof the material of the underlying plies, with the difficulty increasing as the movable line moves inward; under single-ply conditions the difficulty is not present, but where two: or more pliesare secured together, the difficulty increases materially asthe. number of plies increase. As will'be understood, the connection of the tabs does not contemplate'any variation in the length of the apical zone, and hence, under multi-ply line of foldconditions, theactual effect is to place a strain on the adherent connection between tabs through the attempt of'thc inner ply to gain the increase in lengthrequired at its apical zone-the effectbecomes more pronounced as the movable folding line moves inward.

The present invention is designed to mitigate this condition by the specific. arrangement of the end tabs and their particular folding relationships. As shown, both the front face ii and rear face Ill carry end tabs Ha and Mia, respectively, but in fashioning the envelope, these two tabs are not adherently connected together, the adherent connection being between tab lilo and the additional tab section He, the inner face of this section being adherently secured to the outer face of tab ma. Hence, while the two tabs are physically connected through the connection of tab Illa and section Hc, tab ma does not cross the movable line of foldindicated at cZ-but extends practically to it. As a result, the end is completely closed, but the movable line of fold d is therefore of single-ply formation throughout the major length of such movable line, the conditions changing in the end zones of such line, as now to be referred to. The conditions referred to are shown in the Fig. 5 section, in which the folding line is of single-ply formation.

The bottom zone of the bellows-fold is complicated by the necessity for connecting the tabs with the bottom zone of th envelope represented by the sections i2a, 12b; this function is performed by tabs its, this tab being folded upward; since tab It} is first folded inward, the per tion of tab G20 above line a2 is adhesively secured to the outer face of tab llla, after which tab Ha is folded up to overlie and be adhesively secured to the outer face of that portion of tab 120 lying below line (22, section Ho above tab E20 then being adhesively secured to the outer face of tab lea; thus, line a?! of tab life will overliefolding line it and provide a two-ply folding line in the bottom zone, the length of which is represented by the length of tab l2ca greater length than the distance which folding line a2 moves during collapse of the bottom; hence, as shown in Fig. 6, half of tab iZc exposed on the inside of the envelope, with the other half lying between and secured to both tabs ila and Hatab lea remains; exposed on the inner side of the envelope, although it does not overlie the movable folding line represented by lines d and a2. While the dual-ply formation is present within this zone,

10 the strain on" the" adhesive connections is small sincebut one additional =p1y=is-present dueto the fact that tab lea does not cros's the movable folding line, thus leaving a portion of tab 12c exposed, so that the latter tab is connected with tab lid on the inner face-of the latter-and therefore in n alinement with the apex of the folding line dthe opposite portion of tab l2e lies between and is secured to-botlr tabs I027) and section He, and is thus firmly an ho ed againststrain.

The upper zone of-"the movable folding line is also of dual-ply formation on the foldi ng-line, a1:- though both faces Hi and H are marginallyreinforced, including this zone of tabs "la and Ila, flap Mb beinginfold'ed to place section HUG as exposed inside the'envelope; and thus as overlyingthe dual thickness of tab Illa, so that the plies of tab ma" extend between the folding line of tab em and th-e't of section be, thus spacing the two folding lines,- with the latter carried by tab Ha, the dual tab formation or tab ma within this zone being anchoredby the section lie on the outer side and by sectionlllic onthe inner side, thus notonly-providing-a' high- 137 eIhcientreinforciri-g formation for these-marginal zones of faces liiiand H", but prod-ncing'the result with the limited dua1- 1y-rermation of the movable folding line;

In other words, the completed envelope not only presents the-advantages of' the encl bottom support discussed above, but has its upper mouth zone very efliciently reinforced, and obtains this result from the blank itself and by the use of dual-ply zones for the upper and lower zones of the side movable folding line and a single ply for the remainder of such folding line. As a result, the envelope thus formed is extremely durable in construction and therefore of longlife characteristic, highly efficient in service, and is produced entirely from a blank of simple formation and capable of ready production, doing this and providing an envelope having the advantage of the exposed data-carrying zone. fact that not only the upper margins of faces ill and H are re-inforced, in connection with the fact that this reinforcing extends into the upper bellows-fold zones, while the lower zone of the movable folding line is also reinforced, with the reinforcing applied in such manner as to limit the ply thickness of such line within these zones is limited to a dual-ply formation, is an important feature which aids in producing these results.

In other words, with the blank formed from heavy calendered paper-board stock, and fashioned as indicated, the resultant envelope is not only practically indestructible, as to material, but the formation is such as to provide for expansion and collapsing within a wide range, and i for stability at all variations within the range. This is of especial importance where the envelope is of the large dimensions that may be required within this particular filing servicethe dimensions of the rear wall may be 1-0" X 15', a well known filing system dimension, with the envelope expandible to approach a 2" thickness; as the envelope expands through the addition of content, stability remains constant-due to the foot characteristic of the side bellows fold, the fold foot being active in all positions up to maximum expansion, while the removal of the bellows fold characteristics at the sides and bottom with maximum expansion through the complete development of the rectangular arrangement at the bottom and sides provides an angular formation The l l therebetween which preserves stability at such time. Hence, whether the envelope has little or much content, stability of the envelope is maintained.

As will be understood, the fact that the width of extensions 10a and I la is similar and that such width is also equal to the width of the sections I2a and I222, the bellows-fold structures are such that the envelope can be expanded or collapsed uniformly throughout the area of walls I 0 and I I. Such uniformity is not forced by the arrange ment, since the content accumulation may be mainly of small sized documents, but will generally take place, inasmuch as the bottom fold is directly affected and the trend would be that the side folds would also have somewhat similar movements. The advantage lies in the fact that in the latter case, the documents can be more or less distributed within the pocket and may include large sizes, since the ability to provide for this uniformity in movement throughout the area 12 sential insofar as the same may fall within the spirit and scope of the invention as expressed in the accompanying claim, when broadly construed.

What is claimed as new is: In an expansible envelope of the bellows type, a front wall, a rear wall of greater height than the front wall, bellows means connecting the side and bottom edges of said walls, extensions on the top edges of said walls folded inwardly and se cured adhesively to the respective walls, said extensions when so folded having their free transverse edges in the same horizontal plane, and tabs integral with the ends of the rear wall extensions adhesively secured to the bellows means connecting the sides of the front and rear walls.

MORTON J. SHAFFER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 867,789 Bushnell, Jr Oct. 8, 1907 975,792 Pittman Nov. 15, 1910 1,734,642 Olm Nov. 5, 1929 2,188,730 Swab Jan. 30, 1940 2,219,526 McLaren Oct. 29, 1940 2,281,452 Ottinger Apr. 28, 1942 

